<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .nav{
            width: 100px;
            height: 100px;
            background-color: rgb(36, 14, 233);
            /* clear: both; */
            margin: 10px;
            /* 同时清楚两种 */
            /* overflow: hidden;
            clear: both; */

            

        }

        .box1{
            width: 100px;
            height: 100px;
            background-color: red;
            margin: 10px;
            float: left;
        }
    </style>
</head>
<body>
    
        <div class="box1"></div>
        <div class="box1"></div>
        <div class="box1"></div>
        <nav class="nav"></nav>
    
</body>
</html>